Online advertising exchanges (ad exchanges) allow advertisers to present personalized advertisements to target users based on a range of user features relating to different aspects of the users themselves and the users' activities. The performance of the individual advertisements presented at a particular online space with respect to any given combination of the user features may vary along many different measurements, such as click-through rate, impression-to-conversion rate, revenue per conversion, etc. Advertisers may select different combinations of user features and pay different amounts of advertising costs for different types of targeted advertising.